Plyboard adhesive



Dec. 21, 1937. J. v. BAUER I 2,102,937

PLYBOARD' ADHESIVE Filed July 26, 1935 lNVENTOR ATTORNEYS Patented Dec. 21, 1937 UNITED STATES PATENT OFFICE PLYBOARD ADHESIVE Application July 26, 1935, Serial No. 33,206

Claims.

My invention relates toadhesives and more particularly to vegetable types of adhesives containing starch in an ungelatinized or partially ungelatinized form suitable for the purpose of making corrugated paper board.

The usual method of making corrugated paper board is a continuous two step operation. It consists of corrugating a strip of paper by means of heated fluted rolls, applying an adhesive to the tips of the corrugations on one side, bringing a liner in contact with it and forming the bond with the assistance of heat and considerable pressure. This operation may be considered as the first step and forms what is known as a single faced corrugated board, comprising a corrugated strip of paper bonded to a smooth surfaced strip. The second step of the operation consists of applying an adhesive to the tips of the exposed corrugated surface, bringing a liner in contact with it and forming the bond with the assistance of heat and just suflicient pressure to hold the paper surfaces in contact. The result of these two operations is a stiff paper board comprising 7 two smooth outer paper surfaces bonded to an inner core of corrugated paper.

In the manufacture of double faced corrugated board, the adhesive problem is considerably more difficult than that of adhesively combining two or more smooth surfaced strips of paper. In bonding two or more smooth surfaced strips of paper together in a continuous process, it is possible to apply any desired amount of pressure by means of rolls in order to assist the rapid formation of a bond. In the case of corrugated board, however, only a very small amount of pressure can be used to assist the formation of a bond between the single faced board and the second liner because of the danger of crushing the corrugation. As a result, points of poor contact developwhere the corrugation tips do not touch the liner. It thus becomes necessary to apply a sufficient amount of adhesive to the'tips of the corrugations so that there will be suificient adhesive present to completely fill in any points of poor contact between the liner and corrugation tips. In order to compensate for these adverse conditions, it is customarily necessary in using silicate of soda adhesives to heat the board after the second liner has been brought into contact. The heating tends to dry the adhesive and make it set more rapidly. The heatingperiod is relatively short, however, for the machines operate at a high rate of speed, for example, between 175 and 325 feet per minute.

Because of these adhesive problems in connec- (01. lei-23.4)

tion with the manufacture of corrugated paper board, it is necessary that an adhesive used must be capable of a rapid increase in viscosity on the application of heat. When the board passes from the machine the adhesive must be suiiiciently setup to hold the bonded surfaces together and allow the board to be cut and otherwise handled. Up to the present time the only adhesive that possesses this characteristic to a satisfactory degree and is also of low cost is the silicate of soda type. This is truev to the extent that practically all of the present day machines for making corrugated paper board have been designed and built with the idea of using silicate of soda as the adhesive.

In the manufacture of corrugated paper board, it is not essential that the adhesive used should form a bond of extremely high agglutinant strength inasmuch as it is only necessary that the bond be slightly stronger than the paper itself.

The essential feature necessary in an adhesive for double faced corrugated paper board is the ability to rapidly form a bond between two paper surfaces under conditions'of heat and low pressure and possible poor contact between the surfaces.

Gelatinized starches or starch derivatives such as dextrine have previously been used as adhesives but have not been found satisfactory. The reason for the superiority of silicate of soda over such starch adhesives for use with laminated paper such as corrugated paper lies in the fact that silicate of soda adhesives develop a very decided increase in viscosity with a small decrease in their moisture content, whereas in the case of gelatinized starch or starch derivative adhesives, the increase in viscosity is relatively very small with a corresponding decrease in moisture content.

In the manufacture of corrugated board it is not necessary and often not possible that the adhesive bond be completely dry when the board comes off the machine as the complete drying out the paper together at the points 'of contact, it

can be readily seen that under the same conditions of spread,'temperature and moisture absorption by the paper, the silicate of soda adhesive will always form a sufilcient degree of bond in less time than a gelatinized starch adhesive, for example. This is particularly true when the cost situationmakes it necessary to use considerably more water in the starch adhesive than is used in the silicate of sodaadhesive. As a result, gelatinized starch adhesives have never been able to successfully compete with silicate of soda from the standpoint of production speed when 'used on corrugating machines making double faced corrugated board.

Although up to the present time, silicate of soda is the only adhesive that has been commercially practical for the manufacture of cor,- rugated paper, it does possess certain disadvantages and limitations which render it undesirable and to some extent unsatisfactory for use in the manufacture of corrugated board and boxes made therefrom. Among the technical and practical disadvantages and limitations of silicate of soda when used in the manufacture of corrugated paper board products may be mentioned the following:

The commercial grades of sodium silicate are highly alkaline and have a tendency to weaken the fibres and the rosin size in papers, thus weakening the paper and lowering its water resistance. It also has a tendency to stain, discolor, corrode, or dull the finish of the wooden, aluminum, glass and other articles commonly packed in this type of board for shipment. Also, silicate of soda adhesives set in the form of a brittle film which is often fractured or broken when the paper is strained or bent. Because of the above mentioned disadvantages of silicate of soda adhesives, there has been a strong demand for a low priced adhesive which could successfully be used to replace silicate of soda for corrugating purposes. Regardless of this demand, no starch adhesives have been developed up to the present which have been commercially successful.

I have discovered that it is possible to make a starch adhesive for corrugated paper making purposes which is not only competitive with silicate of soda in cost, but also gives superior results, particularly from the standpoint of speed of bond formation.

My adhesive as compared to silicate of soda and previous starch adhesives, enables the corrugated board machines to be operated from 10% to 20% faster than would be otherwise possible.

Unlike silicate of soda, it does not gather in hard deposits in the glue boxes or-on the machine. Likewise, it does not accumulate on the pressure belts and form the usual ridges which cause scoring of the paper. The residual deposits, if any, of adhesive on the heating plates of the machine are not nearly as hard as sodium silicate deposits and will flake off easily, requiring little or no scraping or blowing. My adhesive, because of its non-abrasive character, causes less wear on the bearings and fingers of the machine, the latter remaining cleaner because of the tendency of the adhesive to flow readily off of them.

Because of the low alkalinity of my adhesive as compared to silicate of soda, it is less injurious to the operator's hands. Furthermore, because of the low alkalinity of my adhesive, it does not cause corrosion, staining or tarnishing of the materials wrapped or enclosed in the paper board made with this adhesive.

My adhesive after drying is not as brittle as silicate of soda, and therefore will withstand substantial bending of the paper board without any deleterious results.

An object of my invention is to provide a new and improved type of starch adhesive and process for using the same, not subject to the disadvantages and limitations of the prior adhesives and processes for bonding surfaces, particularly corrugated board. Other objects and advantages of my invention will become apparent from the following description of my invention.

I have discovered that by using ungelatinized starch in conjunction with a suitable carrier or suspension medium as an adhesive for making corrugated board it is possible to obtain a bond the equivalent or better than bonds previously ob tained and at a greater rate of speed. I have found that by the use of my adhesive the disadvantages of the prior adhesives and binding processes are avoided. I have also found that the balance or relationship between the ungelatinized most part independent of the rate at which the moisture in the adhesive is driven off by heat or absorbed by the paper. Rather it is mainly the time required to heat the paper and adhesive to the gelatinization temperature of the suspended ungelatinized starch. Water is taken up by the starch as the starch gelatinizes and the viscosity of the adhesive mixture is raised to such an extent that an immediate bond is formed. Because of the great extent to which the viscosity can be increased by this method, it is possible to use from three to five parts of water to one part of dry material in my type of adhesive and still obtain a sufficient viscosity increase upon the application of heat to bond the paper satisfactorily when it comes off the machine.

I have found that certain types or varities of starch are inherently more suitable for use in my adhesive than others. For example, tapioca, rye, and potato starches are inherently greatly superior to corn, Wheat and rice starches when they are used as the ungelatinized starch portion of the adhesive.

The principal factors that determine the suitability of a starch for the ungelatinized starch portion of my adhesive are as follows:

1. The time required to completely gelatinize the starch in water by means of heat.

2. The temperature at which the starch gelatinizes.

3. The viscosity developed by the starch after gelatinization.

4. The degree of tackiness developed after gelatinization.

It is desirable that a starch for this purpose gelatinize very rapidly so that it will develop a high degree of viscosity in a short length of time. This factor will determine the rate of speed at which the paper can be bonded on the machine.

It is desirable that the starch have a fairly low temperature of gelatinization in order that it will be Within the temperature range developed on the machine. This factor will also determine the speed at which the paper can be bonded on the machine.

factor will largely determine the amount of water that can be used in the adhesive formula. The greater the viscosity developed, the larger the amount of water that may be used, which will reduce the cost. Also the greater the viscosity the greater the strength of the bond which holds the paper together when it comes off the machine. The balance between these factors depends on the type of operation and product desired by the user.

It is desirable that the starch upon gelatinization form a tacky or sticky gel as this tends to insure against breakage of the newly formed bond when the board is handled soon after coming off of the machine.

Tapioca, rye and potato starches seem to have these desirable characteristics to a greater extent than the other common varieties of starch and are preferred for use in my adhesive.

I have found, however, that it is possible to adapt the less desirable starches such as corn,

rice, wheat, sago, etc. to the purposes of my adhesive by the addition of small amounts of caustic soda, which I have found has the effect of increasing the speed of gelatinization and lowering the temperature of gelatinization of these starches. Furthermore, by the addition of small amounts of borax, I have found the viscosity of these starches will be increased to a desirable degree when they are gelatinized. The addition of these chemicals will so improve the characteristics of the above starches that it will bring them within the operating range of the usual corrugating machine for example, and thus permit their successful use for my purpose. When added in the correct proportions, these chemicals may also be used toimprove the operation of tapioca, rye and potato starches in my adhesive.

' In regard to the portion of my adhesive which forms the carrier or suspension medium for the ungelatinized starch portion, it is desirable that this material be of such a nature that it may be prepared with water to form a free flowing solution or colloidal solution of sufllcient viscosity to hold the granules of ungelatinized starch in suspension and also enable the adhesive to be picked up by the rolls of the machine and applied to the paper.

' The more essential features desired in a carrier for my purpose are as follows;

1. It should hold the ungelatinized starch portion of the adhesive in a state of suspension and thus prevent any undue separation or settling out of the ungelatinized starch granules.

2. It should pick up evenly and well on smooth rolls of a corrugating machine, for example, and

viscosity to the adhesive to enable it to function properly, as above described, when three to five parts of water, or such relatively large proportions, are used.

I have found the best carrier for these purposes is a gelatinized starch solution sumciently modified by oxidizing agents or other means such as partial dextrinization, to bring the viscosity characteristics within the desired range.

Several adhesive formulas utilizing the principles of my invention and which I have found in practice to be very satisfactory for combining corrugated board on the present types of corrugating machines are as follows:

FORMULA #1 The carrier portion of the adhesive is prepared as follows:

Blend Per cent Tapioca flour 45 Soda ash 16 Calcium hydrate 12 Barium peroxide. Clay (300 mesh) 26 45 lbs. of this blend are mixed with 168 lbs of cold water for a period of about 30 minutes. During this mixing period the starch in the mixture is gelatinized by the caustic soda formed by the reaction between'the soda ash and lime. Subsequently, this gelatinized starch is acted on by the barium peroxide which thins it out to a smooth fluid consistency. At the end of this time, 1 pint of formaldehyde is added to the mixture to stop any further action of the barium peroxide and the mixture is diluted with an additional 400 lbs. of water. Other aldehydes as well as sulphurous acid, bisulphites or other suitable reducing agents may be substituted for the formaldehyde.

The ungelatinized potentially adhesive base portion of the adhesive contains the following:

' Pounds Tapioca flour; 140 Borax 3 Water 184 These three materials are mixed in a separate container and then added to the carrier, prepared as above. The resulting mixture containing the gelatinized carrier and ungelatinized base is then agitated for about 30 minutes; or until a perfectly homogeneous and free flowing product is obtained. In this condition it is ready for use on the corrugated paper fabricating machine.

The above formula gives approximately 100 gallons of an adhesive product containing ungelatinized tapioca starch "suspended in a carrier medium of modified gelatinized tapioca starch and is a specific example of an adhesive using the principles of my invention that has proven satisfactory in actual practice.

FORMULA #2 The carrier portion of the adhesive is prepared as follows:

Blend Per cent Tapioca flour 45 Soda ash 20 Calcium hydrate 15 Barium peroxide Clay (300 mesh) 19 45 lbs. of this blend are mixed with 163 lbs. of cold water for a period of about 30 minutes. During this mixing period the starch in the mixture is gelatinized by the caustic soda which is formed and is subsequently acted on by the barium peroxide, which thins it out to a smooth .fluid consistency. At the end of this time, 1

m ed

pint of formaldehyde is added and the mixture diluted with an additional 400 lbs. of water.

The ungelatinized potentially adhesive base portion of the adhesive contains the following:

Pounds Corn starch 140 Borax 3 Water 184 These three materials are mixed in a separate container and then added to the carrier. The resulting mixture containing the gelatinized carrier and ungelatinized base is then agitated for about 30 minutes, after which it is ready for use on the machine.

The above formula is similar to Formula #1,

with the exception that instead of tapioca flour, corn starch is used for the ungelatinized starch portion of the adhesive. The amount of soda ash and lime is increased over that used in Formula #1 so as to form a larger amount of caustic soda and thus lower the gelatinization temperature of the corn starch and increase its speed of gelatinization. This formula also has been proven by actual operation on corrugating machines under conditions of commercial operation.

In both of the examples mentioned above, soda ash and lime are used as a convenient means of introducing caustic soda into the formula. The caustic soda thus formed not only acts as a means of gelatinizing the starch in the carrier, but also subsequently acts as a means of lowering the gelatinization temperature and increasing the gelatinization speed of the ungelatinized starch portion of the adhesive when the bond is formed on the machine.

The barium peroxide when used with soda ash and lime has the property of acting on the starch carrier medium at temperatures below 100 F.

and thus it is possible to obtain a gelatinized starch carrier medium of the desirable viscosity characteristics by means of a cold mix. In any of these formulas the barium peroxide may be added in the desired amount to the starch carrier after water has been added.

The clay used in the formula is an inert filler which is not essential to the success of the adhesive. It is used merely to prevent undue lumping up of the carrier mixture when it is added to the water.

The borax used in the formula performs the function of increasing the degree of viscosity develcped by the adhesive on the machine and thus enables the use of the large amounts of water specified in the above formulas.

Several other examples of corrugating adhesives of this type are as follows:

FORMULA #3 35 lbs. of this blend are dispersed in 140 lbs. of cold water. To this mixture are added 2.75 lbs of caustic soda dissolved in 10 lbs. of water. After .the starch gelatinizes, the mixture is agitated about 20 minutes during which time it is thinned out by the action of the barium peroxide to a smooth fluid consistency. At the end of this time, 1 pint of formaldehyde is added and the mixture diluted with an additional 400 lbs. of water.

The ungelatinized potentially adhesive base portion of the adhesive contains the following:

Corn starch pounds 160 sulphonated castor oil pints 1 Borax pounds 2 Water pounds 190 These four materials are mixed in a separate container and then added to the'carrier. The resulting mixture containing the gelatinized carrier and ungelatinized base is then agitated for about 30 minutes, after which it is ready for use on the machine. In this formula, 9. modified gelatinized corn starch is usedas the carrier medium and corn starch is also used for the ungelatinized portion of the adhesive. The sulphonated oil specified in this formula is added to make the adhesive pick up more evenly on the rolls and transfer to the paper better. 'It is not necessary. on some machines, but is desirable on some of the higher speed machines.

genuine #4 50 lbs. of partially dextrinized starch are cooked with 250 lbs. of water. to a temperature of 190 F. and then cooled to a temperature of below 100 F. In a separate container, 100 lbs. of tapioca, rye or potato starch are mixed with 200 lbs. of water and added to the above mixture. The material is then'mixed until homogeneous, after which itis ready to rub on the machine.

An adhesive formula of this type is desirable in cases wherein it is necessary that the adhesive be completely free from'alkaline substances. In this specific instance a cooked "partially dextrinized starch is used as the carrierrnedium. The degree of dextrinization should be such that the final viscosity of the adhesive when mixed up is about the same as that ofi38 to 40 B. silicate of soda.

Either tapioca, rye, or potato starches or blends are specified for the 'ungelatinized starch in this non-alkaline formula because they gelatinize rap idly enough to enable the adhesive to be used satisfactorily on the machines without the necessity of addingcaustic soda'to further increase the speed of gelatinization.

If it is desired to use ,corn starch in a formula of the non-alkaline type, it is usually necessary on high speed machines to add sufficient amounts of such chemicals as: zinc chloride, calcium chloride, urea, formaldehyde, etc. which are non alkaline and yet have the property of lowering the gelatinization temperature of starches, in order to bring the setting time of the adhesive within the speed range ofgrthe machine.

The specific formulas for corrugating adhesives, which I have submitted above, are merely several specific examples that I have found to be satisfactory in actual practice. However, I do not intend my invention to be limited to such specific examples for various modifications and substitutions may be made in them without departing from my invention;-

Although there are considerable dilferences between the various examples as far as specific ingredients and amounts are concerned, the principles involved are the same and they all possess one common essential feature, that is, each composition contains a" certain amount of ungelatinized starch kept-in suspension by means of a suitable carrier or suspension medium.

I appreciate that the Duerden Patent No.

620,756 issued in 1899 discloses the use of starch in water as-a medium for bonding two surfaces upon the application of heat. However, this patent fails to appreciate the necessity for the use of a carrier with the starch to obtain a successfully operative process. For the first time, I have developed an improved and a successful adhesive and a method utilizing ungelatinized'starch as a potential adhesive agent by combining it with a novel carrier or suspension medium having characteristics that permit the application of the adhesive in such a form as to make possible, for the first time, a rapid formation of an effective bond upon the application of heat to gelatinize the starch in situ.

In the corrugating adhesives of my invention, 1 incorporate several new and novel features, referred to below, which are essential factors in making an adhesive of this type commercially practical for use in making corrugated board on the present day types of high speed machines.

I have already noted some of the advantages of my novel combination of starch with a viscous carrier, for example, the increased speed of bonding operation possible; the even distribution of the starch by preventing settling and separation of the starch; the even and sure transfer of the adhesive to the surface to be bonded; the ability of the adhesive to stand on the ridged surfaces I have found that the temperature of gelati-' nization of the ungelatinized starch portion of an adhesive may be lowered if desired and the speed of gelatinization increased. Such lowering of the-gelatinization temperature might be desired, for example, if the natural gelatinization point of a given starch were above the temperature acquired by the surfaces and bonding adhesive passing through a machine. Also it might be found desirable to make more certain that all of the' ungelatinized starch becomes gelatinized during passage in order to secure complete utilization of the adhesive properties of the starch. This lowering of the gelatinization point and increasing the rate, may also be desired for the purpose of increasing the rate at which the pa.- per surfaces can be processed, for an increase in rate of passage would normally result in a lower temperature at the bond. I have found in this connection that caustic soda for example, or such well known starch gelatinizing agents, as zinc chloride, calcium chloride, urea, or formaldehyde, when mixedwith my adhesive in proportions insuflicient to completely gelatinize the ungelatinized starch present, act to lower the temperature of gelatinization of the ungelatinized starch and thus increase the rate of gelatinization for the purposes referred to above.

For example, by this means the gelatinization temperature of the ungelatinized starch component of my adhesive may be adjusted as desired by merely increasing or decreasing the concentration of the starch gelatinizing agent in the adhesive composition. thus making it possible to adapt it to the individual temperature conditions under which it is to be used.

I have found that the use of soda ash and lime in conjunction with barium peroxide is particularly effective as a means for both gelatinizing the starch in the carrier mixture and as a means of thinning out the starch to a more fluid consistency without the necessity of cooking-the mixture or raising its temperature above room temperature. The ingredients, I have found, can be easily mixed with the starch to be-used as the carrier and easily distributed.

Barium peroxide alone or in combination with either caustic soda, lime, or soda ash alone will not thin out the consistency of a viscous starch gel to a sufficiently fluid state without cooking the mixture at a temperature above 140 F.

I have discovered it is possible to cause barium peroxide to act on a heavy viscous starch gel and thin it out to a fiuid consistency at temperatures below 100 F. to 50 F. by using the barium peroxide in combination with soda ash and lime or their equivalents. Somewhat similar results can be obtained by using barium peroxide in conjunction with sodium fluoride and lime, or caustic soda and calcium carbonate as a means of thinning out a starch gel at temperatures below 100 to 50 F. Other equivalent oxidizing agents may be used for example, sodium peroxide, calcium peroxide, and hydrogen peroxide, or others capable of liberating oxygen.

The use of borax in conjunction with the adhesive composition herein described I have found is a desirable means for increasing the viscosity developed by the ungelatinized starch portion-of my adhesive when it is subsequently gelatinized on the machine. By so treating the starch I am enabled to use a greater proportion of water in the adhesive than would otherwise be possible.

Previously borax had not been used with unconverted starches such as undextrinized or unoxidized starches for adhesive purposes, probably because it tended to increase the viscosity of the starch gel to such an extent that the starch could not effectively be applied as an adhesive except in the form of a very dilute solution. Because of the inherently different characteristics of my operation it is now possible to use borax with unconverted starches, the effect of borax on starch in increasing the viscosity of the starch gel being an advantage in my improved adhesive and operation, and enables me to use a greater proportion of water with my adhesive than would otherwise be possible. Other borates as well as boron compounds which react with alkalies to property may be used. Sodium aluminate may also be used for this purpose.

I have also found that sulphonated oils of the type of sulphonated castor oil or. Turkey red oil may be advantageously used in small amounts in conjunction with my adhesives whenever it is desirable or necessary to improve the evenness or smoothness with which the adhesive compositions are picked up on the rolls of the machine and transferred to the paper.

The proportions of carrier material and ungelatinized starch base in my adhesive may be varied through a fairly wide range while still obtaining satisfactory results. For example, a successful adhesive of this type can be made up with as little as 15% ungelatinized starch and as much as 85% carrier material on a dry basis if the amount of water used in the formula is limited to 955 than 2% parts of water to 1 part of the total ,form borates having this viscosity increasing position, or on the basis of the total amount of the water used as little as 3 parts of ungelatinized starch to 50 parts of water. In general, the smallest proportion of ungelatinized starch that can be used in an adhesive composition of this type, is that amount which upon complete gelatinization after being subjected to heat in passage through the fabricating machine will give an apparent and useable increase in viscosity resulting in an immediate adhesive or bonding action.

The greatest proportion of ungelatinized starch that can be used in an adhesive composition of this type is determined by the amount of water used in the formula and by the amount 'of carrier material necessary to give the finished composition sufficient viscosity to operate successfully on the machines, which takes into consideration all of the factors of my adhesive already enumerated.

It is necessary that the viscosity developed by an adhesive composition of this type when its ungelatinized starch component is completely gelatinized on the machine, be suflicient to hold the paper plies together when they come off the machine so they may be cut and handled without breakage of the bond. It is this factor which determines the greatest proportion of water that can be used in an adhesive composition of my type.

The specific formulas I have disclosed herein are examples of what I have found to be good practice inan adhesive of this type. It should be understood, however; that my invention is not limited to these specific examples, but is adaptable to various changes, modifications, and substitutions, the scope of which is to be limited only by the prior art and the appended claims.

An example of the practical application of the adhesive of my invention to the manufacture of laminated corrugated paper board is described below and illustrated in the accompanying drawing in which:

Figure 1 is a diagrammatic representation of a system for making corrugated board using myadhesive as the bonding agent, and

Figure 2 is a perspective view of a laminated corrugated paper board made in accordance with my invention, the top layer of paper being partially separated from the inner core to illustrate the method of uniting.

Referring now to Figure 1. the various mechanisms of this system have been illustrated entirely in diagrammatic form since they are not, per se, a part of this invention. My invention may be carried out by means of various other types of machinery than that illustrated in Figure 1 and furthermore it is not limited to the manufacture of the specific type of corrugated paper board shown in Figure 2 but may be applied to the manufacture of numerous other types of corrugated paper board products, made by similar methods. However, the following description of the operation of the system in Figure 1 will serve to illustrate one specific application of my invention:

The paper, which is to form the core of the corrugated paper board made in the system shown in Figure 1, is stored upon the supply roll l0. During operation, this paper is unwound from the roll Ill and passes between steam jets II, which emit a fiow of steam for moistening and softening the strip of paper I2. After passing through the steam jets H, the strip I2 passes one of the carbohydrate ungelatinized types of adhesive materials, such as those described hereinbefore, by means of the roll i8, which is suspended in the container l9 filled with the adhesive material 20. The adhesive covered roll I! causes a coating of the adhesive to be applied to the convex portions on one side of the corrugated strip of ,paper We passing around the periphery of the roll 5. A little further around the roll [6, the corrugated paper l5a comes in contact with another strip of paper 26, which is to form one of the liners in the final product. This strip of paper 26 is supplied from supply roll 2!, and is brought into contact with the corrugated strip of paper l5a by means of the guide and tension rolls 22, 23, 24 and 25. The roll 25 causes the strip of paper 26 to come into intimate contact with the coated portions of the corrugated strip of paper l5a. on the roll |6, so

that the two strips are caused to be united. The

roll [6 is preferably heated by means of steam for the purpose of drying the'steam-moistened paper I50. and for causing the adhesive to unite the liner strip 26 to the corrugated coil i511.

The corrugated strip live. and the liner 26 united thereto now pass around the roll 21 in such a manner that the uncoated side of the corrugated strip l5a is brought into contact with a second adhesive supply roll 28. This roll 28 is caused to rotate and is supplied with adhesive material by means of the roll 29 suspended in the container 30, which is filled with the ungelatinized adhesive material 3i. The roll 28 applies a coating of my adhesive material to the convex portions of one side of .the corrugated strip l5a in the same manner as the first adhesive-supplying roll l1 coated the reverse side of this corrugated strip. As the corrugated strip l5a, which now has a liner 26 united to one of its surfaces and has an adhesive coating deposited on the ridges of its other surface, leaves the roll 21, it comes into contact with the strip of paper 32 which is to form the other liner. This strip of paper 32 is supplied from the supply roll 33 and is brought into contact with the coated side of the corrugated strip i5a by means of the guide and tension rolls 34, 35, 36 and 31.

After leaving the roll 31, the assembly, comprising the inner corrugated strip of paper [5a, a top liner 32 and a bottom-liner 26 passes between the hot plate 38 and the brushes 39. vThe heat from the hot plate 38 is for the purpose of converting the ungelatinized portion of the adhesive material, which has been previously deposited between the core and the outside liners, to a gelatinized state. This heat treatment so modified the starch adhesive that the viscosity is increased to a point where it becomes effective as a bonding agent and partially dries it. The brushes 39 serve the purpose of keeping the paper board assembly in slight contact with the hot plate 38 during the time of heating.

The rubber covered rolls 40 serve to pull the three strips of paper Ito, 26 and 32, through the entire system. The finished paper board, leaving the rolls 40, is cut to any desired length by means of the cutters 4|.

The hot plate 38 shown in Figure 1, is operated at a temperature of approximately 250 F. to 375 F. The paper board is fed past the hot plate at a rapid rate, which, depending upon the kind of paper being used and also production requirements, varies between 175 to 325 feet per minute. Even at the top speed of 325 feet per minute, the originally ungelatinized adhesive material of my invention will be converted to a gelatinized form and set to form a strong bond between the several pieces of paper of which the board is made.

Referring now to Figure 2, a piece of paper board of the type made in the system of Figure 1 is illustrated. This board comprises a corrugated inner core 42 and two liners l3 and 44. These liners are firmly united to the core by means of the gelatinized adhesive material, converted to that form in situ, a portion of which is shown at 45. The carrier portion of my adhesive acts in some cases to size the paper at the bond, thus forming a better base on each paper surface for the bonding agent. When the adhesive 45 is one of the types which I have described above, and is used for uniting the originally separate pieces of paper in accordance with the method described above in connection with Figure 1, the board will possess the advantages and improvements outlined hereinabove as characteristic of my invention and will be void of the disadvantages and limitations of the prior types of paper board to which reference has previously been made. While I have described only a specific form of product and operation, these are to be considered merely as illustrative of my invention. Other modifications and improvements will probably become apparent to those skilled in this art whichwill be within the scope of my invention. This method is claimed in applicants Patent No. 2,051,025, which was copending with this application. I wish my invention to be limited, therefore, only by the prior art and the appended claims.

I claim:

1. An adhesive composition of matter for corrugated paper board and other laminated paper products, comprising an aqueous suspension of a potentially adhesive inert ungelatinized amylaceous substance and a viscous gelatinized amylaceous carrier therefor, said ungelatinized material being present in the proportion of at least of the total solids on a dry basis and said caraqueous gelatinous amylaceous carrier for said suspension said ungelatinized starch being preseat in the proportion of at least 15% of ungelatinized starch to 85% carrier on a dry basis and the proportion of aqueous medium ranging from 2 /2 to 5 parts of such medium to one part of total solids of ungelatinized starch and carrier.

3. A composition of matter suitable for use for adhesive purposes comprising at least 4.28% of ungelatinized starch and containing not more than 50 parts of water by weight to 3 parts by weight of ungelatinized starch, and containing not more than 17 parts of gelatinized starch to 3 parts of ungelatinized starch on a dry basis, said of starch, whereby the gelatinization temperature of the ungelatinized starchcomponent is modified, and containing in solution an agent selected from the class consisting of the borates and aluminates whereby the degree of viscosity developed by said ungelatinized starch, component upon gelatinization is increased.

4. A composition of matter suitable for use for adhesive purposes comprising at least 4.28% or ungelatinized starch, and containing not more than 17 parts of gelatinized starch to 3 parts or ungelatinized starch on a dry basis, and containing not more than 50 parts of water by weight to 3' parts by weight of ungelatinized starch, said ungelatinized starch being suspended in a gelatinized starch hydrosol carrier medium, said gelatinized starch hydrosol carrier medium being characterized by such proportion of gelatinized starch to water that the resultant viscous hydrosol carries the ungelatinized starch component in suspension without substantial settling out of the ungelatinized starch, said hydrosol containing in solution a proportion of gelatinizing agent sufficient to lower the temperature of gelatinization of the ungelatinized starch.

5. A composition of matter suitable for use for adhesive purposes comprising at least 4.28% of ungelatinized starch and containing not more than 50 parts of water by weight to 3 parts by weight of ungelatinized starch, and containing not more than 17 parts of gelatinized starch to 3 parts of ungelatinized starch on a dry basis, said ungelatinized starch being suspended in a gelatinized starch hydrosol carrier medium, said gelatinized starch hydrosol carrier medium being characterized by such proportion of gelatlnized starch to water that the resultant viscous hydrosol carries the ungelatinized starch component in suspension, without substantial settling out of the ungelatinized starch, said hydrosol containing in solution an agent selected from the class consisting of the borates and aluminates whereby the degree of viscosity developed by said ungelatinized starch component upon gelatinization is increased.

JORDAN V. BAUER. 

